Bell type annealing furnace



A. N. OTIS BELL TYPE ANNEALING FURNACE Filed Nov. 23, 1934 Inventor AHoert N. Ots,

29m wm At't orneg A Panarea Jen. 14, .1936

UNITED STATES- PATENT yOFFICE am ma FURNACE Albert N. ons, senenemamn. Y.. signor to GeneralElectric Company, a corporation of amucaoommvember z3, 1934, serlslrNo. 154x473 My invention relates to' bell type annealing furnaces and particularly to the base portion of such furnaces.

` In the use offurnaces of this Atype for bright annealing it is usual to provide atight. retort or cover for the material to be annealed andv to maintain a suitable nonoxi'dzing gas within it to forma protective atmosphere for the work. The base of the furnace commonly is constructed of brickwork of which the outer portion supportsl the bell of the furnace and the finner or central portion supports the work being annealed. It has been f ound that during those intervals'in which the furnace is cool, such as when it is being recharged, or if it should stand idle for long pe-` riods, considerable air and sometimes moisture is taken upby the brickwork and 'that as the furnace subsequently is reheated this air upon being Idriven oif contaminates .the non-oxidizing atmosphere surrounding the work.

, An attempt was made to overcome this by coverving the brickwork with sheet metal; however, that was not successful, for, due to the great diifen=r. ence in` temperature between the central and the outer portions of the cover, serious warping of the cover occurred which resulted in breaking the welded joints connectingy the different parts 4of the cover.

It is the object of my invention to provide an improved base and sheet metal cover construction which will avoid the yabove mentioned diiculties. Another object is t' provide in such a construction improved' means` for supplying gas to and removinggas from the furnace through the base and cover.

My invention will be better understood-,from the following description taken in connection with the aocompanxsdrawingggf, and fruits scopef. Vwill *be bell is constructed in the conimon and well known manner and is shown comprising the outer metallic casing 2,' the relatively thick base plate 3, the

layer of heat insulation 4 and the lining 5 of sult able refractory material. Mounted on the walls of the inner layer yare shown the electric heating units vWithin the bell the usual internal s claims. (ci. zee-ls) circular retortni-.hood 1 which has the outward flange at its lower portion terminating in a cylindricalportion Il which is'adapted to engage in a trough, to be described later, toform a seal.

. Thebase of the-furnace comprises the. struc- .5

tural steel members vIII, such as'. channel bars shown as supported on other channel bars Il whichfare mounted on track wheels I2 adapted to run on the rails I3. 'I'he base further comprises a metallic plate I5which may be rectangular in 10 form, whichl plate supports the brickwork I6. The latter is surrounded by thecircular sheet metal trough. I1, which-contai'naa suitable sealing liquid such as oil into-which dips the portion 8 ofthe hood. The brickwork4 I6 may be considered as 15 comprising an outer annular portion upon which rests the bell-of. the furnace and the central or pier portion which is adapted to support the work being annealed, the latter' portion being shown as supporting the spider I8 for receiving the work 20 to be annealed, such for example es coils of steel strip.

order to prevent the escape of air from .the brickwork into the furnace when thelatter is reheated after having'beenallowed to cool' 26 down and after having been opened for recharging, I have provided the cover 20 which completely covers the brickwork and is sealed'ln the sealing trough I1. This cover is built up of sheet metal parts welded together in a gas tight manner and 30 'comprises theouter ring-like part 2l which rests upon the bellsupporting portion,of the brickwork and which includes the outer cylindrical part 22 which dips into the trough I1. The centrai part 23 ofthe cover, which part -covers that 85 4portionof thebrickwork supporting the work being annealed, includesa downwardly extend- 4inga'cylinaricai,portieri.inasnmnli as thecentratr l portion of the brickwork is built up to a higher level than the surrounding bell'supporting portion 40 It will beunderstoodthat as the temperature of thefurnaceis brought up to its operating. value, those parts of the cover which are subject to .the full heat of the furnace, such as the parts 45 l23 and 24, undergo considerable expansion,l so that if those parts are welded directly to other parts of the cover, such as lthe part 2| which is more or less protected from the full heat of the furnace, great strains occur at I such points of connection. To avoid the consequent warping of the 'cover" and possible opening ofthe welded joints therein I have provided the -cover with the 7 annular connecting portion 2B. This portion has its inner edge welded tothe lower edge of the 55 part 24 and its outer edge welded to the part 2 I A. The part 26 thereby forms a funnel shaped resilient'connectionbetween the outer and the cen.- tral parts of the cover, the brickwork being provided with an annular channel to receive said connection and the lower edge of part 24. Preferably this connection is curved, being convex,

upwardly, thereby better to yield tothe expan-l sion -and contraction of the other partsof the cover.

Where a furnace of this type is to be usedfor bright annealing, the work being annealed must be surrounded by a protective atmosphere during the annealing operation. For conveying the gas i `of the base where air and oil fumes naturally icc' Letters Patent oftheUnited States is: Y l x collect when the furnace is heated. In each exhaust pipeI include a resilient joint such as a metal bellows shown at 32A inasmuch as the pipe 3| at its lower end is rmly secured to the base plate I5, the upper portion of the pipe 3l ob viously being subject to slight movements due to the connection 26 to which is is welded. The

lower ends of each pipe 30 and 3l is preferably secured to the base plate I5 in the manner shown by Fig. 3. In this figure it will be seen that the sleeve or coupling 34lis'screwed onto the end of the pipe and is enclosed by the ring 35 which is welded to thebase plate I5, a suitable set screw 36 being employed to preventmovement of'- coupling 34 during assembling and disassembling of the apparatus, particularly the lower piping and connections.' The cover plate 31 is bolted to the ring 35 in-a gas tight manner and a short nipple 38, welded to 31, connects this cover plate with coupling 34. An external pipe connection 39 isll coupled with the nipple 38 and in the casepf the inlet pipe connects with a suitable source of protective gas andV in the case of the exhaust pipes may lead to a suitable point of discharge. By the above-described construction, a gas tight connection is made between the inlet and outlet pipes and the base, which connection is highly desirable to avoid any danger of air entering the fur.- nace in the event that a break should occur in the cover.

I have chosen the particular embodiment described above as illustrative of my invention and it will be apparent that various modications may be made without departing from. the spirit and-scope of my invention, which modications I aim to cover by the appended claims.

What I claim as new and desire to secure by aocaioe' rpartssoast ject tothe liberation of air comprising an annular portion constructed to support the bell of the furnace, a central portion constructed to support the work being annealed and an air tight sheet metal cover therefor including parts covering each of said portions and an intermediate resilient part connecting said first mentioned and contraction of said parts.

2. In a bell type annealing furnace, a base subo provide lfor independent expansion lject to the liberation of air comprising an annularportion constructed to support the bell of the furnace, a .central portion constructed to supportthe work being annealed and an air tight sheet metal cover therefor, said cover including a part vcovering said annular portion, a part covering .said central portion and an inclined annular part connecting said first mentioned parts.

3. In a bell type annealing furnace, a base subject to the liberation of air comprising an annular Y portion constructed to support the bell of the furadapted to support the work being annealed, an

airtight sheet metal cover for said brickwork including parts covering said annular and central portions and an intermediate inclined part connecting said parts and a pipe extending through said base and cover, said pipe having gas tight connections with and a yielding portion intermediate said plate and said cover.

5. In a bell type annealing furnace, a base 'comprising a plate and brickwork thereon in- 1. In a bell type annealing furnace, a subbase and cover, means securing the pipe gas tight 

